Trochlear resurfacing system and method

ABSTRACT

A system for repairing a defect on an articular surface of a patient&#39;s trochlear region, the system comprising a guide block comprising a body having an exterior surface configured to engage with the saddle portion and ridge portions of the patient&#39;s trochlear region, a protrusion extending generally from the body and configured to be received in a first bore formed in the articular surface along a reference axis, and a first cavity extending through the body configured to establish a first working axis displaced from the reference axis, wherein the exterior surface of the body and the protrusion are configured to secure the location of the guide block about the patient&#39;s trochlear region. A method for preparing an implant site in bone, comprising: establishing a reference axis extending from the bone; creating a bore in the bone by reaming about the reference axis; securing a guide block about the articular surface; establishing a first working axis extending from the bone using the guide block, the first working axis is displaced from the reference axis; and creating a first socket in the bone by reaming about the first working axis, wherein the first socket partially overlaps with the bore.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/153,113, filed May 12, 2016, which is a continuation of U.S. patent application Ser. No. 13/785,867 (now U.S. Pat. No. 9,351,745), filed Mar. 5, 2013, which is a continuation of U.S. patent application Ser. No. 12/713,135 (now U.S. Pat. No. 8,388,624), filed Feb. 25, 2010, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/155,390, filed Feb. 25, 2009 and entitled Trochlear Resurfacing System and Method, which is fully incorporated herein by reference. U.S. patent application Ser. No. 12/713,135 (now U.S. Pat. No. 8,388,624), filed Feb. 25, 2010, is also a continuation-in-part of U.S. patent application Ser. No. 12/397,095 (now U.S. Pat. No. 7,896,883), filed Mar. 3, 2009, entitled Femoral Condyle Resurfacing System and Method, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/033,136, filed Mar. 3, 2008, entitled Femoral Condyle Resurfacing System and Method. U.S. patent application Ser. No. 12/713,135 (now U.S. Pat. No. 8,388,624), filed Feb. 25, 2010, is also a continuation-in-part of U.S. patent application Ser. No. 10/373,463 (now U.S. Pat. No. 7,678,151), filed Feb. 24, 2003, entitled System and Method for Joint Resurface Repair. U.S. patent application Ser. No. 12/713,135 (now U.S. Pat. No. 8,388,624), filed Feb. 25, 2010, is also a continuation-in-part of U.S. patent application Ser. No. 12/027,121 (now U.S. Pat. No. 8,177,841), filed Feb. 6, 2008, entitled System and Method for Joint Resurface Repair and is a continuation-in-part of U.S. patent application Ser. No. 11/169,326 (now U.S. Pat. No. 8,361,159), filed Jun. 28, 2005, entitled System for Articular Surface Replacement. The entire disclosures of all of which are incorporated fully herein by reference.

FIELD

This disclosure relates to devices and methods for the repair of defects that occur in articular cartilage on the surface of bones, particularly the knee.

BACKGROUND

Articular cartilage, found at the ends of articulating bone in the body, is typically composed of hyaline cartilage, which has many unique properties that allow it to function effectively as a smooth and lubricious load-bearing surface. When injured, however, hyaline cartilage cells are not typically replaced by new hyaline cartilage cells. Healing is dependent upon the occurrence of bleeding from the underlying bone and formation of scar or reparative cartilage called fibrocartilage. While similar, fibrocartilage does not possess the same unique aspects of native hyaline cartilage and tends to be far less durable.

In some cases, it may be necessary or desirable to repair the damaged articular cartilage using an implant. While implants may be successfully used, the implant should have a shape substantially corresponding to the articular cartilage proximate the area where the implant is to be placed in order to maximize the patient's comfort, minimize damage to surrounding areas, and maximize the functional life of the implant.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention are set forth by description of embodiments consistent with the present invention, which description should be considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic diagram illustrating an incision proximate the knee;

FIG. 2 is a schematic diagram illustrating the femur;

FIG. 3 is a perspective view of one embodiment of a drill guide consistent with the present disclosure;

FIG. 4 is a perspective view of one embodiment of the drill guide on the articular surface to establish the reference axis consistent with the present disclosure;

FIG. 5 is a perspective view of one embodiment of a pin and the articular surface consistent with the present disclosure;

FIG. 6 is a perspective view of one embodiment of a contact probe disposed about the articular surface consistent with the present disclosure;

FIG. 6A is a close-up of region 6A in FIG. 6 consistent with the present disclosure;

FIG. 7 is a perspective view of one embodiment of a contact probe along the inferior-superior and medial-lateral planes consistent with the present disclosure;

FIG. 8 illustrates one embodiment of a sizing card consistent with the present disclosure;

FIG. 9 is a perspective view of one embodiment of a surface reamer consistent with the present disclosure;

FIG. 10 is a perspective view of one embodiment of a surface reamer aligned with a guide pin and a drill consistent with the present disclosure;

FIG. 11 is a perspective side view of one embodiment of a guide block consistent with the present disclosure;

FIG. 12 is a perspective view of one embodiment of a guide block and securing pins consistent with the present disclosure;

FIG. 13 is a perspective view of one embodiment of a guide bushing consistent with the present disclosure;

FIG. 14 is a perspective view of one embodiment of a guide block and a guide bushing received therein consistent with the present disclosure;

FIG. 15A and FIG. 15B are perspective views of an implants consistent with the present disclosure;

FIG. 16 is another perspective view of one embodiment of the implant shown in FIG. 15 consistent with the present disclosure;

FIG. 17 is a top end perspective view of one embodiment of the implant shown in FIG. 15 consistent with the present disclosure;

FIG. 18 is a bottom end perspective view of one embodiment of the implant shown in FIG. 15 consistent with the present disclosure; and

FIG. 19 is a cross-sectional view of one embodiment of the guide block shown in FIG. 11 consistent with the present disclosure.

DETAILED DESCRIPTION

According to one embodiment, the present disclosure may feature a system and method for resurfacing at least a portion of an articular surface having a defect by replacing a portion of the articular surface with an implant. The implant may comprise a load bearing surface having a contour and/or shape substantially corresponding to the patient's original articular surface about the defect site which may be configured to engage an adjacent articular surface. The present disclosure will describe a system and method for replacing a portion of the articular surface of the trochlear region; however, it should be understood that the system and method according to the present disclosure may also be used to resurface articular surfaces other than the trochlear region.

As an initial matter, many of the devices described herein comprise cannulated components configured to be arranged over other components. The degree to which the cannulated passageway (i.e., internal diameter of the passageway/cavity) of a first component corresponds to the external diameter of the component over which it is being placed may be close enough to generally eliminate excessive movement. Excessive movement may be defined as an amount of movement that may result in misalignment of the implant relative to the articular surface.

Turning now to FIGS. 1 and 2, an incision 10 may be created proximate the patient's knee 12 (only the femur of which is illustrated for clarity) using a cutting instrument 18 (e.g., a surgical knife) to provide access to the defect 14 on the patient's articular surface 16, for example, as taught in U.S. Patent Application Ser. No. 61/033,136, filed Mar. 3, 2008, entitled FEMORAL CONDYLE RESURFACING SYSTEM AND METHOD, which is hereby fully incorporated by reference. As generally illustrated in FIG. 2, the defect 14 may be generally located within the trochlear region of the knee 12 generally between the lateral and medial condyles 13 a, 13 b. More specifically, the defect 14 may be generally located at a region that cooperates with a patellar (not shown for clarity).

Once the incision is created, a drill guide 20, FIG. 3, may be advanced against the articular surface 16, for example, in the general area of the trochlear region. The drill guide 20 may include a cannulated shaft 22, a proximal end 23 comprising a first and second groove contacting tip 24 a, 24 b configured to contact or engage with the articular surface 16 in the base or lower region 15 of the trochlear region (generally illustrated in FIG. 1). The first and second groove contacting tip 24 a, 24 b may optionally include a generally “C” like shape which may be fixedly coupled to the cannulated shaft 22 and may include a first and second tip 30 a, 30 b configured to contact the articular surface 16 at two different points generally along the inferior-superior plane.

The drill guide 20 may also include a first and second ridge contacting tip 26 a, 26 b configured to contact or engage with the articular surface 16 on the ridges 17 a, 17 b generally defined by the lateral and medial condyles (generally illustrated in FIG. 1). The first and second ridge contacting tips 26 a, 26 b may optionally include a generally arcuate shape extending generally radially outwardly and away from the cannulated shaft 22. The first and second ridge contacting tip 26 a, 26 b may also be moveably coupled to the cannulated shaft 22 and may be biased towards an extended position as generally illustrated in FIG. 2 using a spring or the like (not shown). The first and second ridge contacting tip 26 a, 26 b may be configured to at least partially contact the articular surface 16 at two different points on the ridge generally along the medial-lateral plane.

Because the tips 24 a, b and 26 a, b are moveable with respect to each other, the drill guide 20 may be advanced against the articular surface 16 until a portion of the tips 24 a, 24 b contact the articular surface 16 generally along the inferior-superior plane of the articular surface 16 and the tips 26 a, 26 b contact the articular surface 16 generally along the medial-lateral (ML) plane of the articular surface 16. The four points of contact of the tips 24 a, b and 26 a, b of the drill guide 20 may be proximate, but generally not within, the defect site 14 and may be used to establish a reference axis extending generally approximately normal to the articular surface 16 about the defect site 14, for example, as generally described in U.S. Patent Application Ser. No. 61/033,136. The four points of the drill guide 26 a, 26 b, 30 a, and 30 b may be configured asymmetrical to the axis of shaft 22 to create a repair site that would cover slightly more of the lateral facet of the trochlear groove.

With the four points of the drill guide 20 against the articular surface 16, a threaded guide pin 34, FIG. 5, may be advanced through the cannulated drill guide 20 along the reference axis and into the bone beneath the defect site 14, for example using a drill or the like. The guide pin 34 may include one or more indicia 36 (for example, but not limited to, laser markings or the like) on the shaft 38 of the guide pin 34 that may be used to control the depth of the guide pin 34 into the bone. By way of example, the indicia 36 on the guide pin 34 may be set relative to the length of the drill guide 20 such that the depth of the guide pin 34 is set when the indicia 36 is aligned with the distal end of the drill guide 20. Once the guide pin 34 is coupled to the bone, the drill and the drill guide 20 may be removed leaving just the guide pin 34 coupled to the bone and extending along the reference axis (i.e., substantially normal/perpendicular to the original articular surface about the defect site 14 as generally illustrated in FIG. 4). It should be noted that the cannulated passageway of the drill guide 20 may have an internal diameter substantially corresponding to the outer diameter of the guide pin 34, for example, as generally described in U.S. Patent Application Ser. No. 61/033,136.

Next, measurements of the patient's articular surface 16 may be taken in order to determine the appropriate contour of the implant, FIGS. 6-8. For example, one or more contact probes 50 may be advanced over the guide pin 34 established in the articular surface 16. The contact probe 50 may comprise a cannulated shaft 52 and an outrigger 54 extending radially outwardly and axially outwardly from a distal end of the cannulated shaft as generally taught in U.S. Patent Application Ser. No. 61/033,136. A first and a second contact probe 50 may be provided having outriggers 54 extending radially outwardly at a two different distances. The distances of the outriggers 54 may be dependent upon the size of the implant to be delivered as well as the geometry of the defect site 14 and/or the articular surface 16.

The contact probe 50 may also include measuring indicia 60, which may optionally be disposed in a portion of a handle 58. The measuring indicia 60 may include a plurality of measurement markings indicating relative distances. In use, the contact probe 50 may be placed over the guide pin 34 such that the distal end 62 of the outrigger 54 contacts the articular surface 16. A measurement may be taken by based on the alignment of at least one marking 64 on the centering shaft (for example, the second end of the centering shaft) with the plurality of measurement markings 60.

A first (and optionally a second) measurement of the patient's articular surface 16 proximate the defect site 14 may be taken along the inferior-superior plane using the first contact probe 50 by placing the distal end 62 of the outrigger 54 against the patient's articular surface 16. In addition, a first (and optionally a second) measurement of the patient's articular surface 16 proximate the defect site 14 may be taken along the ML plane using the second contact probe 50 by placing the distal end 62 of the outrigger 54 against the patient's articular surface 17 a, 17 b. The size of the outriggers 54 may be selected based on the size of the defect site 14 such that the distal end 62 of the outrigger 54 contacts the articular surface 16 and not the defect site 14.

The measurements obtained from the contact probes may be recorded onto a sizing card 70, FIG. 8, as generally taught in U.S. Patent Application Ser. No. 61/033,136. The sizing card 70 may include an area graphically representing the inferior-superior and the ML planes. In particular, a first and a second query box may be provided to fill in the first and second inferior-superior measurements and a first and a second query box may be provided to fill in the first and second ML measurements. The query boxes may optionally be connected by a circle representing the size of the outrigger of the first contact probe while the other query boxes may optionally be connected by a circle representing the size of the outrigger of the second contact probe. The sizing card may also include additional query boxes provided to fill in the maximum values of the inferior-superior plane and the ML plane, respectively.

Based on the maximum values of the inferior-superior and ML plane in query boxes, the offset values of the implant and test implant may be determined. The surgeon may select from a set of implants having predetermined offset values. The values correspond to the inferior-superior measurement, ML measurement, and depth of the implant/test implant. It should be noted that the offset values of the implant/test implant may be used in combination with known geometrical ratios of the articular surface for a particular region of the articular surface. These geometric ratios may be found in published literature and may be utilized, for example, when the implant is placed proximate the interface between the posterior and distal regions of the articular surface. If further accuracy is desired (for example, but not limited to, defects extending further towards the posterior region and/or the anterior regions of the articular surfaces), the contour of the implant and articular surface may be determined as described in U.S. patent application Ser. No. 12/027,121 entitled System and Method for Joint Resurface Repair filed Feb. 6, 2008, which is fully incorporated herein by reference.

Turning now to FIGS. 9-10, the diameter of a surface reamer 80 may be selected based on, for example, the maximum ML value. The surface reamer 80 may include a cannulated shaft 82 configured to be disposed over the guide pin 34 along the reference axis and coupled to a drill 81. The surface reamer 80 may also include one or more cutting surfaces 84. The reamer 80 may have a specific geometry or pattern to minimize vibrations and improve tactile feel while negotiating an interrupted cut on the trochlear groove.

The surface reamer 80 may be advanced over the guide pin 34 along the reference axis. The surface reamer 80 may include an indicia 86 (for example, an opening/window, laser marker, or the like) configured to control the depth of the bore B formed in the saddle or base 15 of the trochlear region. For example, the indicia 86 may include a laser marking or the like configured to be aligned with the articular surface 16. The indicia 86 may also include an opening/window or the like which may be aligned with an indicia on the guide pin. The cutters 84 may optionally be positioned about the surface reamer 80 to leave more material proximate the guide pin 34 along the reference axis to facilitate removal and insertion of devices further along the method. Once the articular surface 16 has been excised about the reference axis, the surface reamer 80 and the guide pin 34 may be removed.

A guide block 90, FIG. 11, may be selected based on the measurements taken previously of the patient's articular surface 16. The guide block 90 may be used to establish one or more working axis (for example, a superior and inferior working axis) for excising the articular surface 16 on either side of the reference axis along the superior-inferior plane. The guide block 90 may include a body 92 having a generally arcuate shaped exterior surface generally configured to engage with the base or saddle 15 and ridges 17 a, 17 b of the trochlear region 16. For example, a portion of the guide block 90 have an outer surface which is substantially the inverse of the articular surface 16 which is to be replaced in the trochlear region proximate the defect site 14.

The guide block 90 may further comprise a protrusion or tab 91 extending generally outwardly from the bottom or base surface 93 of the body 92. The protrusion 91 may be configured to be received in the bore B formed by the excision device in the articular surface 16 discussed above. As may be appreciated, the bore B may be formed in the base or saddle 15 of the trochlear region 16. According to at least one embodiment, the protrusion 91 and the bore B may have form a generally interference-like fit such that movement of the guide block 90 may be minimized when the protrusion 91 is received in the bore B.

Turning now to FIG. 12, the guide block 90 may also include one or more securing pins 94, 95 configured to further reduce movement of the guide block 90 relative to the articular surface 16. The pins 94, 95 may be configured to extend through passageways 96, 97 in the body 92 and may be secured (for example, but not limited to, screwed) into the knee. The pins 94, 95 may optionally be secured into the knee in regions which are generally not involved in the articulation of the patellar.

As may be appreciated, the position of the guide block 90 may be generally fixed relative to the articular surface 16 by virtue of the protrusion 91 received in the bore B formed in the articular surface 16, the pins 94, 95, and/or the outer surface configuration of the body 92 generally contacting the trochlear groove.

With the guide block 90 fixed/secured to the articular surface 16, additional excision sites may be formed for receiving the implant. For example, one or more guide bushings 98 may be used as generally illustrated in FIG. 13. The guide bushing 98 may include a passageway 99 configured to receive the shaft 82 of the excision device 80. The guide bushing 98 may be configured to receive the shaft 82 such that the cutters 84 are disposed proximate the distal region 100 of the guide bushing 98. The distal region 100 of the guide bushing 98 may also be configured to be received in a cavity 101 formed in the guide block 90 as generally illustrated in FIG. 14.

According to at least one embodiment consistent herein, the cavity 101 and the distal region 100 of the guide bushing 98 may be configured to threadably engage each other. Alternatively, the cavity 101 and the distal region 100 of the guide bushing 98 may fit together in a generally interference-type connection. While the cavity 101 and the distal region 100 of the guide bushing 98 are illustrated having a generally circular or cylindrical cross-section, the cavity 101 and the distal region 100 of the guide bushing 98 may also include other cross-sectional shapes. For example, the cavity 101 and the distal region 100 of the guide bushing 98 may include a non-circular cross-sectional shape configured to generally prevent movement (rotational and/or translational) movement relative to each other. The guide bushing 98 may optionally include a handle portion 102 configured to facilitate coupling and decoupling of the guide bushing 98 with the cavity 101.

The guide block 90 may also include an opening configured to allow the cutter 80 to pass through the guide block 90 and into the articular surface 16 to form additional excision sites corresponding to the implant to be delivered. When received within the guide block 90, the guide bushing 98 may generally align the longitudinal axis L of the cutter 80 with the articular surface 16 at a predetermined angle relative to the working axis defined by the guide pin. The guide bushing 98 may generally minimize movement of the cutter 80 in any direction except along the predetermined angle with respect to the working axis.

According to at least one embodiment consistent herein, the guide block 90 may be configured to create at least one excision site partially overlapping with the primary excision site (i.e., the excision site corresponding to bore B). As illustrated in FIG. 14, the guide block 90 is shown configured to receive a first and second guide bushing 98 (which may be the same or different) and may form a first and second additional excision site (each partially overlapping with the primary excision site bore B). The guide block 90 may, however, be configured to receive fewer or greater than two guide bushings 98 depending on the size and shape of the implant to be delivered as well as the particulars of the patient's anatomy. In addition, one or more of the additional excision sites formed with the guide block 90 may overlap only an adjacent additional excision site (i.e., one or more of the additional excision sites may not overlap with the primary excision site).

Once the excision sites are formed in the patient's articular surface 16, an implant sizing trial may be selected based on the measurements taken of the articular surface 16. The implant sizing trial may comprise a shape/contour generally corresponding to the shape/contour of the implant to be delivered. The implant sizing trial may comprise a threaded opening configured to be concentrically disposed about the working axis. The threaded opening may also be configured to be threadably engaged with a cannulated shaft/handle. Once the implant sizing trial is inserted into the excision sites in the articular surface 16, the fitment of the implant sizing trial along the inferior-superior and ML planes may be confirmed visually.

With the implant sizing trial inserted within the excision sites and the fitment confirmed, a cannulated pilot drill may be advanced through the handle and the implant sizing trial into the bone along the reference axis. The pilot drill may also include a depth control device such as, but not limited to, a marking (e.g., a laser marking or the like). With the cannulated pilot drill secured in the bone, the implant sizing trial and handle may be removed and the guide pin may be advanced through the cannulated passageway of the pilot drill into the bone along the reference axis. Again, the depth of the guide pin may be controlled by way of a marking (e.g., a laser marking or the like) along the shaft of the guide pin. For example, the depth of the guide pin may be set once the laser marking is flush with the end of the pilot drill.

A cannulated step drill may be advanced over the pilot drill and the guide pin into the articular surface 16 about the reference axis. The use of the pilot drill and the cannulated step drill may be configured to incrementally provide a larger opening in the bone about the reference axis in the articular surface 16 to reduce the potential of chipping the bone about the reference axis. The cannulated step drill may also include a depth stop for controlling the depth of the step drill into the bone.

Once the depth of the step drill is set, the step drill and the pilot drill may be removed and a cannulated tap may be advanced over the guide pin. The depth that the tap is advanced into the bone may be controlled based on a marking (e.g., a laser marking) on the guide pin. The tap may be configured to provide a threaded opening in the bone about the reference axis to threadably receive the implant post as will be described below.

With the opening about the reference axis tapped, the tap may be removed and a tapered post may be advanced over the guide pin at least partially into the threaded opening, for example, using a hex driver or the like. The tapered post may include a tapered and threaded first end and a second end having a tapered exterior surface, for example, as described in U.S. Pat. Nos. 6,520,964, 6,610,067 and 6,679,917, all of which are fully incorporated herein by reference. The second end may also include a hex-shaped internal cavity configured to engage with a corresponding hex-shaped driver of the hex driver. Both the tapered post and the hex driver may be cannulated such that they may be advanced over the guide pin.

The tapered post may be advanced along the guide pin and partially inserted into the threaded opening in the bone (for example, approximately half way) using the hex driver. According to one embodiment, the tapered post may be inserted in the threaded opening such at least most of the threaded end is within the threaded opening. Once the tapered post is partially received in the threaded opening, the hex driver may be removed

The implant sizing trial may optionally be placed into the excision sites. The second end of the tapered post may at least partially extend through the threaded opening of the implant sizing trial. Using the hex driver, the implant sizing trial may be fully advanced into the threaded opening. The hex driver may include a flared end which may engage a shoulder disposed about the opening in the implant sizing trial. The engagement of the flared end and the shoulder may control the final depth of the tapered post into the threaded opening in the bone.

Once the tapered post is fully advanced into the threaded opening, the hex driver and implant sizing trial may be removed. Optionally, a cannulated reamer may be advanced over the guide pin to remove any excess material about the reference axis. The depth of the reaming may be controlled when the shoulder of the reamer contacts the end of the tapered post. The reaming may be provided to extra material left about the reference axis during the reaming discussed above. This extra material may have been left to prevent accidental chipping during the subsequent operations. After the final reaming, the reamer and the guide pin may be removed leaving behind only the tapered post in the bone.

An implant 170, FIGS. 15-18, may be selected base on the measurements taken of the patient's articular surface 16. As discussed previously, the implant 170 may have a load bearing surface 171 including a contour based on the measurements taken of the patient's articular surface 16 such that the load bearing surface 171 generally corresponds to the patient's original articular surface 16, for example, as best illustrated in FIG. 17. In particular, the load bearing surface 171 may include a first curvature 181 (that may include multiple curves) based on or corresponding to the curvature of the articular surface 16 being replaced along the inferior-superior plane in base or saddle portion 15 of trochlear region. The load bearing surface 171 may also include a second curvature 182 (that may include multiple curves) based on or corresponding to the curvature of the articular surface 16 being replaced along the ML plane in ridge 17 a, 17 b portion of trochlear region. The second curvature 182 may include a curve string generally perpendicular to and swept along the length of the first curvature 181 and may vary along the length of the first curvature 181.

According to one embodiment, the implant 170 may include an implant as described in U.S. patent application Ser. No. 10/373,463 filed Feb. 24, 2003, U.S. Pat. No. 6,679,917 issued Jan. 20, 2004, U.S. Pat. No. 6,610,067 issued Aug. 26, 2003, U.S. Pat. No. 6,520,964 issued Feb. 18, 2003, and U.S. Provisional Application Ser. No. 60/201,049 filed May 1, 2000, all of which are fully incorporated hereby incorporated by reference.

The bone facing surface 172 of the implant 170 may a plurality of regions revolved about the plurality of axis established by the guide pin and/or the guide block 90. For example, the bone facing surface 172 may include a contour substantially corresponding to the contour of the plurality of excision sites created in the patient's bone. Because these excisions sites may be created by a rotary cutter moving along the axes established by the guide pin and/or the guide block 90 (e.g., generally normal to the articular surface), the contours of the excision sites may be different than a planar cut (i.e., an excision site created by making a planar or tangential cut across the articular surface). The bone facing surface 172 may optionally include indicia 176 representing either inferior and/or superior sides of the implant 170 as well as the size of the implant 170. These indicia 176 may be used by the surgeon to properly align the implant 170 along the inferior-superior and ML planes within the excision sites. The implant 170 may be inserted into the excision site using a grasping device such as, but not limited to, a suction cup coupled to a handle.

The implant 170 may include a first fixation device 177 coupled to the bone facing surface 172. The first fixation device 177 may be configured to be received in the bore B formed in the articular surface 16. The first fixation device 177 may optionally be configured to engage with a second fixation element configured to be secured into the patient's bone.

For example, the second fixation element may include a post. The post may include a tapered cross-section and may optionally include a threaded outer region configured to engage with the patient's bone as discussed herein. The post may also include one more protrusion or flanges configured to engage with the patient's bone. The first and second fixation element may be configured to be coupled to each other as discussed in U.S. patent application Ser. No. 10/373,463 filed Feb. 24, 2003, U.S. Pat. No. 6,679,917 issued Jan. 20, 2004, U.S. Pat. No. 6,610,067 issued Aug. 26, 2003, U.S. Pat. No. 6,520,964 issued Feb. 18, 2003, and U.S. Provisional Application Ser. No. 60/201,049 filed May 1, 2000, all of which are fully incorporated hereby incorporated by reference. The first fixation device 177 of the implant 170 may include a female opening 185 configured to frictionally engage with a tapered second end of the tapered post.

The bone facing surface 172 may also optionally include one or more rims, ribs or protrusions 180 extending generally downwardly and away from the bone facing surface 172, for example, as illustrated in FIG. 18. For example, the rims 180 may include a superior rim 180 a disposed proximate the superior end region 181 of the implant 170 and/or an inferior rim 180 b disposed proximate the inferior end region 182 of the implant 170. The excisions sites corresponding to the rims 180 may be include a contour configured to receive the rims 180 (which may be formed by the excision cutter 80 and/or may be formed separately).

An adhesive (such as, but not limited to, bone cement or the like) may be applied to the bone facing surface 172 by way of a dispenser, for example a dispenser as described in U.S. patent application Ser. No. 12/031,534 entitled Bone Cement Delivery Device filed on Feb. 14, 2008 which is fully incorporated herein by reference. The female opening 185 of the implant 170 may receive and frictionally engage with the tapered second end of the tapered post. For example, the implant 170 may be mated in the excision sites and to the tapered post using an impactor and hammer.

Turning now to FIG. 19, a cross-sectional view of one embodiment of a guide block 90 is illustrated. As may be seen, the guide block 90 may include one or more cavities 101 configured to receive the guide bushings 98. For example, the cavities 101 may include a threaded region 190 configured to engage with a corresponding threaded region 191 of the guide bushings 98 (for example, the threaded region 191 illustrated in FIG. 13). The guide block 90 may also include one or more openings or apertures 193 configured to allow the cutting head of the excision device 80 to pass through the guide block 90 and into the articular surface below the guide block 90.

According to one aspect, the present disclosure may feature a system for repairing a defect on an articular surface of a patient's trochlear region. The system may comprise a guide block comprising a body having an exterior surface configured to engage with the saddle portion and ridge portions of the patient's trochlear region. A protrusion may extend generally from the body and may be configured to be received in a first bore formed in the articular surface along a reference axis. A first cavity may extend through the body configured to establish a first working axis displaced from the reference axis. The exterior surface of the body and the protrusion may be configured to secure the location of the guide block about the patient's trochlear region.

According to another aspect, the present disclosure may feature a method for preparing an implant site in bone, comprising: establishing a reference axis extending from the bone; creating a bore in the bone by reaming about the reference axis; securing a guide block about the articular surface; establishing a first working axis extending from the bone using the guide block, the first working axis is displaced from the reference axis; and creating a first socket in the bone by reaming about the first working axis, wherein the first socket partially overlaps with the bore.

As mentioned above, the present disclosure is not intended to be limited to a system or method which must satisfy one or more of any stated or implied object or feature of the present disclosure and should not be limited to the preferred, exemplary, or primary embodiment(s) described herein. The foregoing description of a preferred embodiment of the present disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described to provide the best illustration of the principles of the present disclosure and its practical application to thereby enable one of ordinary skill in the art to utilize the present disclosure in various embodiments and with various modifications as is suited to the particular use contemplated. All such modifications and variations are within the scope of the present disclosure. 

What is claimed is:
 1. A system for replacing a portion of an articular surface of a patient's trochlear region, said system comprising: an implant including: a load bearing surface comprising a first curvature and a second curvature, said first curvature extending along an inferior-superior plane in a saddle portion of said trochlear region and said second curvature extending along a medial-lateral plane in a first and second ridge portion of said trochlear region; a bone facing surface comprising a plurality of overlapping regions, each region including a surface contour revolved around an axis; and a first fixation element disposed about said bone facing surface; and a post configured to be secured into bone, said post including a second fixation element configured to be removably coupled to said first fixation element.
 2. The system of claim 1, wherein said first curvature comprises a plurality of curves.
 3. The system of claim 1, wherein said second curvature comprises a plurality of curves.
 4. The system of claim 1, wherein said second curvature includes a curve string generally perpendicular to and swept along a length of said first curvature.
 5. The system of claim 1, wherein said plurality of overlapping regions of said bone facing surface correspond to a first and a second excision site formed in said patient's trochlear region.
 6. The system of claim 5, further comprising a guide block configured to form said first and said second excision sites, said guide block comprising: a body having an exterior surface configured to engage with the saddle portion and ridge portions of said patient's trochlear region; and a first and a second passageway extending through said body along a first and a second axis, respectively, wherein said first and said second axis are displaced from said each other and said first and said second excision sites are revolved around said first and said second axes, respectively.
 7. The system of claim 6, wherein said body includes a base portion and sidewall portions having a generally arcuate shaped exterior surface generally configured to engage with the saddle portion and ridge portions of said patient's trochlear region, respectively.
 8. The system of claim 6, wherein said implant comprises a first and a second segment each having a center corresponding to said first and second passageway of said guide block, said first and said second segment each comprising an arcuate perimeter defined by a cutting head of one or more reamers rotating about said first and second axes, wherein said second segment partially overlaps said first segment on a first end region of said first segment.
 9. The system of claim 8, wherein said first segment defines a first truncated circular geometry.
 10. The system of claim 9, wherein said second segment defines a second truncated circular geometry.
 11. The system of claim 8, wherein said implant comprises at least a third segment partially overlapping with said at least said second segment.
 12. The system of claim 11, wherein said first segment defines a first end of said implant and said third segment defines a second end of said implant.
 13. The system of claim 1, wherein said bone facing surface further includes indicia for aligning said implant with respect to said articular surface.
 14. The system of claim 1, wherein said post includes a threaded outer region configured to engage with bone.
 15. The system of claim 1, wherein said post includes one or more protrusions configured to engage with bone.
 16. The system of claim 1, wherein said first fixation element includes a female opening configured to frictionally engage with a tapered second end of said post.
 17. The system of claim 1, wherein said first fixation element and said second fixation element include a tapered connection.
 18. The system of claim 1, wherein said bone facing surface include one or more rims.
 19. The system of claim 1, wherein said bone facing surface include one or more rims disposed proximate a superior end region and/or an inferior end region of said implant.
 20. The system of claim 19, wherein said bone facing surface include one or more rims disposed proximate a superior end region and an inferior end region of said implant.
 21. The system of claim 1, wherein said bone facing surface has an overall non-planar geometry.
 22. The system of claim 1, wherein each of said plurality of overlapping regions of said bone facing surface is radially symmetrical about said axis. 